1. Field of the Invention
The present invention relates a double row ball bearing in which a first ball row is fitted into one of two rows of raceways respectively formed by an inner race and an outer race before the outer race is mounted onto the inner race and, after the outer race is mounted onto the inner race, a second ball row is fitted into the other raceway in a state where the axes of the inner and outer races are inclined with respect to each other.
2. Description of the Related Art
Conventionally, as a double row ball bearing, in Japanese Patent Unexamined Publication No. 57-6125 of Showa, there is disclosed a unit bearing 60 with a flange. As shown in FIGS. 3 and 4, into one 63 (that is, the raceway 63 which is located near the flange and, in FIG. 3, is situated on the left side) of two rows of raceways 63 and 64 respectively formed by an inner race 61 and an outer race 62, there are fitted a plurality of balls 65 and a retainer 66 before the outer race 62 is mounted onto the inner race 61, and, into the other raceway 64 (the raceway 64 which is located distant from the flange and, in FIG. 3, is situated on the right side), there are fitted a smaller number of balls 67 than the number of the balls 65 and a retainer (not shown) after the outer race 62 is mounted onto the inner race 61.
In other words, in the unit bearing 60 with a flange, at first, after the balls 65 and retainer 66 are fitted into one raceway 63, the outer race 62 is mounted onto the inner race 61. Next, the respective axes of the inner race 61 and outer race 62 are inclined with respect to each other to thereby produce such a state as shown in FIG. 3, so that, between the inner race 61 and outer race 62, there is formed such a crescent-shaped clearance 68 as shown in FIG. 4. And, through this crescent-shaped clearance 68, the balls 67 are fitted into the other raceway 64. Here, the number of the balls 67 to be fitted into the other raceway 64 is smaller than the number of the balls 65 to be fitted into one raceway 63. After then, the balls 67 are distributed equally within the other raceway 64 and the retainer is inserted into the other raceway 64.
Also, referring to FIG. 5, in Japanese Patent Unexamined Publication No. 57-69112 of Showa, there is disclosed a double row angular ball bearing 70 in which the above-mentioned crescent-shaped clearance 68 (see FIG. 4) is formed in a larger size and the number of balls to be fitted into the other raceway 72 is thereby increased.
That is, in the double row angular ball bearing 70, the inside diameter of the end portion (shown on the left side in FIG. 5) of the raceway groove 75 of an outer race 74 forming one raceway 71 into which a large number of balls 73 are to be fitted is set larger than the inside diameters of the remaining portions of the raceway groove 75 by 5% or more of the diameter of the balls.
However, in both of the above-mentioned conventional double row ball bearings 60 and 70, after the outer races 62, 74 are mounted onto their associated inner races 61, 76 respectively, the balls 67 are fitted into the other raceways 64, 72 respectively while the axes of the inner races 61, 76 are inclined with respect to the axes of their associated outer races 62, 74 respectively. Therefore, the balls 67 are easy to swerve from the other raceways 64, 72.
In other words, referring to FIG. 6, a clearance G is defined between the ball-fitting-direction forward side (in FIG. 6, the lower side) edge portion 83a of the raceway groove 83 of the inner race 80 forming the other raceway 82 and the ball-fitting-direction forward side edge portion 84a of the raceway groove 84 of the outer race 81 forming the other raceway 82, in a state where the axes of an inner race 80 and an outer race 81 are inclined with respect to each other after the outer race 81 is mounted onto the inner race 80. Then, the maximum value of the clearance G is larger than the diameter H of the respective balls 85 to be fitted into the other raceway 82. Due to this, the respective balls 85 are easy to swerve away from the other raceway 82. Therefore, there exists a problem that it takes much labor and time to incorporate the balls into the bearing, which in turn increases the cost of the bearing.